<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        *{
            padding: 0;
            margin: 0;
        }
        main{
            width: 800px;
            height: 400px;
            border: 1px solid red;
            margin: 50px auto 0;
            display: flex;
        }
        div{
            width: 100px;
            height: 100px;
            background-color: rgb(32, 131, 212);
        }

    </style>
</head>
<body>
    <main>
        <div>1</div>
        <div>2</div>
        <div>3</div>
        <div>4</div>
    </main>
</body>
</html>